Field of the Invention
This disclosure relates to compositions of doped diamond-like carbon (DLC) coatings, and methods of depositing doped DLC coatings onto substrates. In particular, this disclosure relates to the deposition of grey cast iron-doped DLCs onto substrates.
Description of Related Art
In any system involving mechanical contact (e.g., piston-ring assemblies in an internal combustion engine, tool dies in a lathe, etc.), the reduction of friction and wear of contact surfaces is highly desirable. This reduction can be effected by the use of lubricants and/or surface coatings.
The use of amorphous carbon coatings is a well-established field. Generally, carbon coatings have a high melting point, high hardness, chemical and electrical inertness, high smoothness, and high density. Amorphous carbon coatings may be deposited by a variety of methods, including cathodic arc evaporation, plasma enhanced chemical vapor deposition, chemical vapor deposition, reactive magnetron physical vapor deposition, and non-reactive magnetron physical vapor deposition.
Amorphous carbon coatings may be hydrogenated, for example, by physical vapor deposition in the presence of a reactive gas such as methane or acetylene (i.e., reactive physical vapor deposition). Hydrogen termination of dangling carbon bonds on a coating surface lower friction coefficients, but limits the surface interaction with lubricants designed for ferrous surfaces.
Amorphous carbon coatings with a high sp3 carbon content are considered “diamond-like” carbon (DLC) coatings. Such coatings offer lower friction and wear characteristics at the expense of adhesion to ferrous materials (e.g., steel). To address this, metallic interlayers or transition layers are applied to the substrate before DLC deposition.